Archive for the ‘Neuroscience and consciousness’ Category

Mitochondria ion channels

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The primary function of mitochondria is to generate ATP that supplies cells with energy. Mitochondria are cell organelles comprising an outer and inner membrane, the latter enclosing a matrix space in which hydrogen and electrons are extracted. The inner membrane contains the respiratory chain; the energy from oxidation/reduction reactions is used to move protons out of the inner matrix and across the inner membrane. This establishes an electrochemical potential gradient across the membrane which allows the synthesize of ATP from ADP.

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Consciousness as a meta-phenomenon

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The year is 1954.

Alan Turing, is returning home from work at the University of Manchester where he is using the recently installed Ferranti Mark 1 computer to further his researches on morphogenesis and other matters. This behemoth of a machine with 4,000 valves, 2,500 capacitors, 15,000 resistors, 100,000 soldered joints and 6 miles of wire boasts a huge 5120 bit random access CRT memory, 72kbytes of magnetic drum storage and can carry out over 800 additions every second; but for Turing this is not nearly enough. He dreams of the day when a computer can play chess as well as he can and can even fool us into thinking that it might be conscious. After all, isn’t the human brain just a computer with nerves instead of valves?

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Implicate order

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Bohm argued that both relativity and quantum theory meant that any analysis of the physical world into distinct, well-defined parts was no longer relevant. He suggests that the structure of holograms gives an insight into his concept of undivided wholeness.

In his description of holograms, coherent light from a laser passes through a half-silvered mirror, with part of the beam falling onto a photographic plate, while the other part illuminates a particular structure. Light reflected from this structure also reaches the plate where it interferes with the light waves arriving from the half-silvered mirror. When this photographic plate is lit by laser light a wave front is created, which is seen to have a similar form to the light coming off the illuminated structure. This allows an observer to see the whole of the structure in three dimensions. If only a small part of the photographic plate is illuminated, the whole structure is still visible although less sharply defined.

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Orbitofrontal cortex

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The paper focuses mainly on the lateral orbitofrontal. Orbitofrontal damage can lead to difficulties in switching from behaviours that were previously advantageous, but have ceased to be so. However, the ability to make an initial discrimination, as opposed to altering an existing one, is usually unaffected. Nevertheless, changes in response are not seen as a core function of the orbitofrontal, and damage to the orbitofrontal is seen to effect a range of other tasks.

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Reality, perception, physics

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Thoughts on Reality An insubstantial pageant The one thing we can be reasonably sure of is that what we see has nothing to do with reality. Physics tells us as much as that; that there are no things and there is no colour green. Visual information is delivered to the retina by photons fluctuating at varying frequencies. The photons are either reflected from or produced by ‘objects’, which can in their turn be understood as quantum particles held together by the charges of the electromagnetic Read more […]

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Mechanisms of anaesthesia

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General anaesthetic photolabels are used to find the molecular binding sites of anaesthetics, such as GABA receptors, protein kinase and tubulin. Involvement of anaesthetics with voltage-dependent channels for negative ions and the mitochondria has been demonstrated by photolabelling. At clinical concentrations anaesthetics can effect the functioning of proteins. Photolabels can attach to residues or individual molecules lining protein pockets, and thus indicate the presence of a dynamic ligand in a pocket.

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Anaesthetics and brain energy

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Brain regions where there is an increase in functional energetic demand have a corresponding increase in glucose metabolism, their metabolic rate for oxygen and their cerebral blood flow. Cerebral energy is seen as depending on the oxidation of glucose. Cerebral blood flow similarly tracks energy consumption.

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Conscious perception

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A recent study by Aaron Schurger of the Swiss Federal Institute of Technology suggests that for conscious perception to occur brain activity has to be stabilised for some hundreds of milliseconds. In Schurger’s study, subjects saw a red-on-green line drawing in one eye, but a green-on-red drawing in the other eye.

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Empathy in mammals

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The article discusses studies which seek to know whether empathy can motivate behaviours in non-human mammals. Peggy Mason et al at the University of Chicago showed that rats would free other rats distressed by being held in a restraint. This looked like empathy, but it is possible to argue that the rats really wanted to obtain a playmate rather than relieve another’s distress as such.

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Brain’s Resting State

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The brain’s resting state activity accounts for about 80% of its energy consumption. Anaesthesia, in which consciousness is removed, involves a 40-50% reduction in energy consumption, implying that part of the resting state’s high level of energy consumption is used to sustain consciousness. The resting state also overlaps with the reward system which is based on midline structures, as distinct from lateral regions that are more involved in planning and reasoning.

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